Android之基於AssetManager實現換膚方案

AssetManager的addAssetPath負責將另外一個apk的資源文件加載進當前應用，這裏因爲是api隱藏方法，採用反射方式調用。

查看 addAssetPath方法註釋，容許傳遞的路徑爲資源目錄或者zip文件。

/**
 * Add an additional set of assets to the asset manager.  This can be
 * either a directory or ZIP file.  Not for use by applications.  Returns
 * the cookie of the added asset, or 0 on failure.
 * {@hide}
 */

經過實例化的AssetManager對象，生成插件包對應的Resources對象，拿到該對象便可操做插件包的相關資源文件。

private Resources pluginRes;//插件Resource對象
private String pluginApkPackageName;//插件Apk的包名

public ResPluginOnAssetManagerPattern initManager(Context curContext, String pluginApkPath) throws IllegalAccessException, InstantiationException, NoSuchMethodException, InvocationTargetException, PackageManager.NameNotFoundException, ClassNotFoundException {
    AssetManager assetManager = AssetManager.class.newInstance();
    Method addAssetPath = assetManager.getClass().getMethod("addAssetPath", String.class);
    addAssetPath.invoke(assetManager, pluginApkPath);

    Resources curAppRes = curContext.getResources();
    pluginRes = new Resources(assetManager, curAppRes.getDisplayMetrics(), curAppRes.getConfiguration());
    pluginApkPackageName = UtilsSystem.getPackageNameThroughApkPath(curContext, pluginApkPath);
    return this;
}

想要獲取插件包的資源，能夠經過如下方式引用(這裏僅給出string以及drawable的調用方式，其餘資源相似)：

/**
 * 獲取ResID
 *
 * @param resName
 * @param resType
 * @return
 */
private int getResId(String resName, String resType) {
    if (pluginRes != null && !UtilsString.isEmptyBaseTrim(pluginApkPackageName)) {
        return pluginRes.getIdentifier(resName, resType, pluginApkPackageName);
    }
    return -1;
}

@Override
public String getString(String resName) {
    return pluginRes.getString(getResId(resName, "string"));
}

@Override
public Drawable getDrawable(String resName) {
    return pluginRes.getDrawable(getResId(resName, "drawable"));
}

源碼地址：https://github.com/xiaoxuan948/AndroidUnityLab/tree/master/unity_base_dev_helper/src/main/java/com/coca/unity_base_dev_helper/plugin

來自爲知筆記(Wiz)